In a typical electrical distribution system, electrical energy is generated by an electrical supplier or utility company and distributed to consumers via a power distribution network. The power distribution network is the network of electrical distribution wires which link the electrical supplier to its consumers. Typically, electricity from a utility is fed from a primary substation over a distribution cable to several local substations. At the substations, the supply is transformed by distribution transformers from a relatively high voltage on the distributor cable to a lower voltage at which it is supplied to the end consumer. From the substations, the power is provided to residential and industrial users over a distributed power network that supplies power to various loads. Such loads can include, for example, mechanical motor drives for any of a variety of applications, lights, heating units, HVAC and other environmental applications, computing systems, and a range of other industrial and residential appliances and systems.
At the consumer's facility, there will typically be a protective relay, energy device or other electrical energy meter (“revenue meter”) connected between the consumer and the power distribution network so as to measure the consumer's electrical demand. The revenue meter is an electrical energy measurement device which accurately measures the amount of electrical energy flowing to the consumer from the supplier. The amount of electrical energy measured by the meter is then used to determine the amount for which the energy supplier should be compensated.
Typically, the electrical energy is delivered to consumers as an alternating current (“AC”) voltage that approximates a sine wave over a time period. The term “alternating waveform” generally describes any symmetrical waveform, including square, sawtooth, triangular, and sinusoidal waves, whose polarity varies regularly with time. The term “AC” (i.e., alternating current), however, almost always means that the current is produced from the application of a sinusoidal voltage, i.e., AC voltage. The expected frequency of the AC voltage, e.g., 50 Hertz (“Hz”), 60 Hz, or 400 Hz, is usually referred to as the “fundamental” frequency. Integer multiples of this fundamental frequency are usually referred to as harmonic frequencies.
While the fundamental frequency is the frequency that the electrical energy is expected to arrive with, various distribution system and environmental factors can distort the fundamental frequency, i.e., harmonic distortion, can cause spikes, surges, or sags, and can cause blackouts, brownouts, or other distribution system problems. These problems can greatly affect the quality of power received by the power consumer at its facility or residence as well as make accurate determination of the actual energy delivered to the consumer very difficult.
In order to solve these problems, devices have been developed to provide improved techniques for accurately measuring the amount of power and quality of power used by the consumer so that the consumer is charged an appropriate amount and so that the utility company receives appropriate compensation for the power delivered and used by the consumer. In addition, devices have been developed to provide protection for electrical distribution by switching off loads that fall outside of set electrical parameters or protecting loads from electrical distribution that falls outside of set electrical parameters. Examples of such energy metering, power quality, and protective relay systems are well known in the art.
While these conventional energy device systems provide information about the quality of the power, i.e., frequency and duration of blackouts, brownouts, harmonic distortions, surges, sags, swells, imbalances, huntings, chronic overvoltages, spikes, transients, line noise, or the like, received by a power consumer at a particular consumer site, they fail to monitor and quantify the power quality with a sufficient level of detail. Blackouts, brownouts, harmonic distortions, surges, sags, swells, imbalances, huntings, chronic overvoltages, spikes, transients and line noise are all examples of power quality events. As utility companies become more and more deregulated, these companies will likely be competing more aggressively for various consumers, particularly heavy power users, and the quality of the power received by the power consumer is likely to be important. This, in turn, means that accurate and detailed reporting and quantification of power quality events and overall power quality will become more and more important as well.
As detailed reporting and operation of these devices is necessary, current technology typically uses random access memory (RAM) to store data. However, current technology of battery backed-up static RAM (BBSRAM) require replacement of a battery and threaten complete loss of memory if the battery fails. Battery backed-up SRAM suffers from higher cost and limited life because of the battery which is needed to retain the data in memory when the system power is off. The life of this backup battery will be affected by temperature which puts restriction of the use of this memory. Current flash memory has a limitation of speed as well as a limitation on the number of erase cycles. While flash memory file systems combined with volatile RAM is a possible solution, this can be very difficult and expensive to design, as the device must try to save data in the flash system from the volatile operating memory before the microprocessor stops operating and the volatile memory is lost. Other standard memory technologies also have limitations. Dynamic RAM (DRAM) is volatile and difficult to integrate, Static RAM (SRAM) is high cost and volatile, and flash has slower writes and limited memory endurance. Accordingly, there is a need for a device or revenue meter to retain measured data, calculated data, and user data in the event of a catastrophic power quality event such as a complete control power failure of the meter, relay, or power quality device.